Chemical States Analysis of Trace-boron by using an Improved SEM-SXES

Abstract

X-rays originate form electronic transitions from valence bands (bonding electron states) to inner-shell electron levels inform us elementally specific chemical states in materials. The energies of those X-rays range from about 0.1 to a few keV, soft X-ray region. Thus, soft X-ray emission spectroscopy (SXES) based on electron microscopy (EM) can be a sensitive tool for elemental and chemical identifications of specified specimen areas. For that purpose, a grating spectrometer for SXES-EM has been realized as a commercial instrument with an energy resolution of 0.2-0.3 eV at Al-L emission (73 eV) [1,2].A test SXES-SEM instrument with a micro-channel plate (MCP) detector combined with a CMOS camera has been applied for state analyses of bulk specimens [3]. It performed an energy resolution of 0.13 eV at Al-L emission. To improve the energy resolution of the system, the MCP with a channel pitch of 15 m has changed to a new one with that of 7.5 m. Optical component between the MCP and the CMOS camera was readjusted in its magnification. Figure 1 shows Al L-emission spectra of a bulk specimen obtained by the improved system in photon counting mode. A small step of L 2 -edge (E F to L 2 -shell) and a large L 3 -edge (E F to L 2 -shell) is clearly resolved. The energy resolution evaluated from the L 3 -edge by taking into account the thermal broadening of Fermi distribution function is 0.08 eV, which is better than that of the previous one. Although the energy resolution has improved, it takes a longer acquisition time to have a good signal to noise ratio in photon counting mode compared to that of analog integration mode. Thus, analog integration mode has adopted for the present trace-boron analysis, unfortunately the energy resolution is a few times lower than that of photon counting mode. Figure 2 shows an SEM image of a carbon steel specimen. Average contents of B, P, and C are 45, 53, and 41 ppm (wt.%), respectively. The image shows several precipitates with different sizes and shapes are distributed in the matrix. The SXES spectra obtained from the numbered areas in figure 2 are shown in figure 3. Accelerating voltage, probe current and acquisition time were 5 kV, 170 nA and 5 min, respectively. The spectrum of area 3 (matrix area without any precipitates) shows mainly C-K and O-K signals, which may originate from contamination and oxidation of the specimen surface, respectively. It should be noted that there is no apparent B-K intensity in the spectrum. On the other hand, spectra obtained from precipitate areas show characteristic peaks and show different features each other. Area 1 shows mainly C-K and a little B-K. Area 2 shows a dominant B-K and smaller N-K and S-L. Area 4 shows B-K and S-L. Area 5 shows a dominant B-K and small N-K and Si-L. It can be noticed that spectra with dominant B-K intensity, 2 and 5, also show apparent N-K and O-K intensity. O-K intensity of those spectra is larger than that of area 3, matrix without any precipitate. Those results suggest a presence of boron nitride and boron oxi...

Information of Valence Charge of 3d Transition Metal Elements Observed in L-Emission Spectra

“…On the other hand, Lℓ,emission due to transitions from a shallow inner-shell of M1(3s1/2) to a deeper inner-shell of L2,3 can give different information from that of L emissions [1]. Here, L-emission spectra of 3d transition metal elements from Sc to Zn and some oxides were measured to examine a relation between L-emission intensities of L Lℓ,and a number of 3d electrons (N3d) of those elements by using a soft X-ray emission spectrometer attached to a scanning electron microscope [2,3]. For aiming a quantitative evaluation, spectral intensities were detected by a MCP detector in photon counting mode, which means that the integrated intensity of an emission peak corresponds to a number of emitted X-ray photons or related electronic transitions in a specimen examined [4].…”

Na–Ga–Si type-I clathrate single crystals grown via Na evaporation using Na–Ga and Na–Ga–Sn fluxes

“…The structures of Si/Ga cages containing Na were depicted using VESTA. 21 So X-ray emission (SXE) spectra were measured using an SXE spectrometer attached to a port of a wavelengthdispersive spectrometer of a scanning electron microscope (SEM, JEOL, JSM-6480LV 22,23 ). The electric resistivities of the single crystals were measured from 10 to 300 K using the fourterminal method with Ag paste electrodes.…”

Chemistry of zipping reactions in mesoporous carbon consisting of minimally stacked graphene layers

“…SXES was performed on an original SXES attached to a scanning electron microscope of JSM-6480LV. 29,30 A varied-line-spacing grating, JS200N, with an average groove density of 1200 lines per mm, was used in these experiments. Because the acceptable energy range of this spectrometer is limited, the second-order spectrum of C Kemission, C-K(2), was measured.…”